To investigate the effects of intake port and combustion chamber on in cylinder flow field of gasoline engine

a simulation analysis was carried out based on a 1.4 L MPI gasoline engine. First

a model covering intake port

intake valve

intake valve seat

combustion chamber and piston was built and verified by the engine bench test. Then the steady numerical simulation of the intake port and combustion chamber of the engine and transient numerical simulation of the intake and combustion processes at 2800 r/min

the condition of the lowest brake specific fuel consumption(BSFC)

were conducted using the AVL-FIRE software. The take port and combustion chamber were optimized based on the simulation results. Four simulation schemes were put forward: the optimized port + the optimized piston with a protrusion on intake side(scheme 1)

the optimized port + the optimized piston with a large radii recess(scheme 2)

the original port + the original piston + increased compression ratio(scheme 3)

and the original port + the original piston(scheme 4). The comparison analysis was performed of in cylinder velocity fields

turbulent kinetic energy fields

flame surface densities and transient heat releases of the four schemes. The results show that the optimized intake port has a much greater tumble ratio than the original intake port; the scheme 1 can best maintain tumble

has the best turbulence distribution and the highest turbulent kinetic at ignition

and has the quickest flame spread and combustion compared with the other three schemes. The optimization of intake port and combustion chamber can enhance in-cylinder air motion

increase turbulent intensity at ignition

speed up the propagation of flame

and improve combustion process.